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The WHO dengue classification and case definitions: time for a reassessment. [Clasificación del dengue y definición de casos de la OMS: tiempo de una nueva evaluación]
Lancet. 2006 Jul 8; 368(9530):170-173.Dengue is the most prevalent mosquito-borne viral disease in people. It is caused by four dengue virus serotypes (DEN-1, DEN-2, DEN-3, and DEN-4), of the genus Flavivirus, and transmitted by Aedes aegypti mosquitoes. Infection provides life-long immunity against the infecting viral serotype, but not against the other serotypes. Although most of the estimated 100 million dengue virus infections each year do not come to the attention of medical staff , of those that do, the most common clinical manifestation is non-specific febrile illness or classic dengue fever. About 250 000--500 000 patients developing more severe disease. The risk of severe disease is several times higher in sequential than in primary dengue virus infections. Despite the large numbers of people infected with the virus each year, the existing WHO dengue classification scheme and case definitions have some drawbacks. In addition, the widely used guidelines are not always reproducible in different countries--a quality that is crucial to effective surveillance and reporting as well as global disease comparisons. And, as dengue disease spreads to different parts of the globe, several investigators have reported difficulties in using the system, and some have had to create new categories or new case definitions to represent the observed patterns of disease more accurately. (excerpt)
Evaluation of the World Health Organization standard tourniquet test and a modified tourniquet test in the diagnosis of dengue infection in Viet Nam.
Tropical Medicine and International Health. 2002 Feb; 7(2):125-32.A positive tourniquet test is one of several clinical parameters considered by the WHO to be important in the diagnosis of dengue hemorrhagic fever, but no formal evaluation of the test has been undertaken. As many doctors remain unconvinced of its usefulness, this study was designed to assess the diagnostic utility of both the standard test and a commonly employed modified test. A prospective evaluation of the standard sphygmomanometer cuff tourniquet test, compared with a simple elastic cuff tourniquet test, was carried out in 1136 children with suspected dengue infection admitted to a provincial pediatric hospital in southern Vietnam. There was good agreement between independent observers for both techniques, but the sphygmomanometer method resulted in consistently greater numbers of petechiae. This standard method had a sensitivity of 41.6% for dengue infection, with a specificity of 94.4%, positive predictive value of 98.3% and negative predictive value of 17.3%. The test differentiated poorly between dengue hemorrhagic lever (45% positive) and dengue lever (38% positive). The simple elastic tourniquet was less sensitive than the sphygmomanometer cuff, but at a threshold of 10 petechiae (compared with the WHO recommendation of 20) per 2.5 sq. cm the sensitivity for the elastic tourniquet rose to 45% (specificity 85%). Other evidence of bleeding was frequently present and the tourniquet test provided additional information to aid diagnosis in only 5% of cases. The conventional tourniquet test adds little to the diagnosis of dengue in hospitalized children. The simple, cheap elastic tourniquet may be useful in diagnosing dengue infection in busy rural health stations in dengue endemic areas of the tropics. A positive test should prompt close observation or early hospital referral, but a negative test does not exclude dengue infection. (author's)